An orthogonal architecture is a kind of connection structure popularly used in a current communications system to connect a main control component and several functional components. Such orthogonal architecture of single boards may be implemented by using a single board arrangement manner of vertically inserting a front board and horizontally inserting a rear board, or horizontally inserting a front board and vertically inserting a rear board. In the foregoing implementation manner, a heat dissipation system generally uses design of a Z-shaped air duct. By taking a manner of horizontally inserting a front board and vertically inserting a rear board as an example, as shown in FIG. 1, single boards include a front board 11 and a rear board 12, which are respectively inserted on two sides of a backplane 14 in a chassis 10. The front board 11 is horizontally inserted, and the rear board 12 is vertically inserted. When the system works, a fan 15 blows air outward so as to drive air from an air intake vent 13 at a bottom of the chassis 10 to enter the chassis 10. In a direction indicated by arrows shown in FIG. 1, air passes through heating components 121, 122, and 123 on the rear board 12, then passes through heating components 124, 125, and 126, and is blown outward by the fan. In this way, temperature concatenation between an upper component and a lower component on the rear board is formed, thereby directly affecting a heat dissipation effect of the heating components 124, 125, and 126 close to a top. In addition, because the system uses design in which air enters from the bottom and exits from the top, a 4U air intake vent space and a 4U air outlet space need to be reserved, thereby occupying a relatively large space area.